Data transmitter

ABSTRACT

A data transmitter includes an encoder configured to encode first data to be transmitted, in accordance with an encoding rule and a transmitter configured to transmit the encoded first data. The encoder makes a change to the encoding rule, encodes the first data in accordance with the change in the encoding rule, and incorporates second data having content corresponding to the change in the encoding rule, into the first data.

INCORPORATION BY REFERENCE

The present invention is based upon and claims the benefit of priorityfrom Japanese patent application No. 2017-062788, filed on Mar. 28,2017, the disclosure of which is incorporated herein in its entirety byreference.

TECHNICAL FIELD

The present invention relates to a data transmitter and, in particular,to a data transmitter that transmits two types of data through the sametransmission path.

BACKGROUND ART

In addition to primary data to be transmitted from a transmitter to areceiver, for example, data desired by the receiver, such as atransmission error detected by the transmitter or the state of thetransmitter, may need to be transmitted. The primary data to betransmitted needs to be transmitted at high speed, and such data will behereafter referred to as “high-speed data.” On the other hand, otherdata does not need to be transmitted at high speed and can betransmitted at lower speed than the high-speed data, and such data willbe hereafter referred to as “low-speed data.”

Consider two independent devices 1, 2 between which high-speed data istransmitted as described above. If low-speed data which is informationabout the state of the device 1 is transmitted from the device 1 to thedevice 2 in this configuration, two typical methods below areconceivable.

A first method is to provide a transmission medium L1 for transmittingdata and another transmission medium L2 for transmitting informationabout the state of the device, as shown in FIG. 1. In this method, themedium for transmitting data and the medium for transmitting informationabout the state of the device are independent of each other andtherefore information about the state of the device can be transmittedwithout blocking data transmission.

A second method is to transmit information about the state of the devicethrough a data transmission medium L1, as shown in FIG. 2. As shown inFIG. 3, this method involves transmitting primary data to betransmitted, which is high-speed data, and information about the stateof the device, which is low-speed data, in a time-sharing manner.Methods for transmitting multiple types of data using a time-sharingtechnique are described in, for example, Patent Documents 1, 2, 3.

-   Patent Document 1: Japanese Unexamined Patent Application    Publication No. 2009-016925-   Patent Document 2: Japanese Unexamined Patent Application    Publication No. 2001-127799-   Patent Document 3: Japanese Unexamined Patent Application    Publication No. 2000-124929

SUMMARY OF THE INVENTION

Unfortunately, the first method needs to provide a dedicatedtransmission medium for transmitting information about the state of thedevice, causing a problem that the equipment cost is increased. Thesecond method involves transmitting data in a time-sharing manner,causing a problem that the transmission efficiency of high-speed data isreduced.

The problem associated with the second method can occur not only whenpieces of data having content as described above are transmitted butalso when multiple pieces of data of any types are transmitted throughthe same transmission path.

Accordingly, an object of the present invention is to solve the aboveproblems, that is, the increase in equipment cost and the reduction indata transmission efficiency associated with the transmission ofmultiple pieces of data.

A data transmitter according to one aspect of the present inventionincludes:

an encoder configured to encode first data to be transmitted, inaccordance with an encoding rule; and

a transmitter configured to transmit the encoded first data.

The encoder makes a change to the encoding rule, encodes the first datain accordance with the change in the encoding rule, and incorporatessecond data having content corresponding to the change in the encodingrule, into the first data.

A data receiver according to one aspect of the present inventionincludes:

a receiver configured to receive first data encoded in accordance withan encoding rule; and

a decoder configured to decode the first data in accordance with theencoding rule.

If a change is made to the encoding rule in encoding the first data, thedecoder detects the change in the encoding rule by decoding the firstdata and reads second data having content corresponding to the change inthe encoding rule.

A communication system according to one aspect of the present inventionis a communication system including a data transmitter and a datareceiver.

The data transmitter includes:

an encoder configured to encode first data to be transmitted, inaccordance with an encoding rule; and

a transmitter configured to transmit the encoded first data.

The encoder makes a change to the encoding rule, encodes the first datain accordance with the change in the encoding rule, and incorporatessecond data having content corresponding to the change in the encodingrule, into the first data.

The data receiver includes:

a receiver configured to receive the first data encoded in accordancewith the encoding rule; and

a decoder configured to decode the first data in accordance with theencoding rule.

If a change is made to the encoding rule in encoding the first data, thedecoder detects the change in the encoding rule by decoding the firstdata and reads second data having content corresponding to the change inthe encoding rule.

A data transmission method according to one aspect of the presentinvention includes:

encoding, by a data transmitter, first data to be transmitted, inaccordance with an encoding rule; and

transmitting, by the data transmitter, the encoded first data.

The data transmitter makes a change to the encoding rule, encodes thefirst data in accordance with the change in the encoding rule, andincorporates second data having content corresponding to the change inthe encoding rule, into the first data.

A data receiving method according to one aspect of the present inventionincludes:

receiving, by a data receiver, first data encoded in accordance with anencoding rule; and

decoding, by the data receiver, the first data in accordance with theencoding rule.

If a change is made to the encoding rule in encoding the first data, thedata receiver detects the change in the encoding rule by decoding thefirst data and reads second data having content corresponding to thechange in the encoding rule.

A data transmission/reception method according to one aspect of thepresent invention is a data transmission/reception method performed by acommunication system including a data transmitter and a data receiver.

The method includes:

encoding, by a data transmitter, first data to be transmitted, inaccordance with an encoding rule;

transmitting, by the data transmitter, the encoded first data, whereinthe data transmitter makes a change to the encoding rule, encodes thefirst data in accordance with the change in the encoding rule, andincorporates second data having content corresponding to the change inthe encoding rule, into the first data;

receiving, by a data receiver, the first data encoded in accordance withthe encoding rule; and

decoding, by the data receiver, the first data in accordance with theencoding rule, wherein if a change is made to the encoding rule inencoding the first data, the data receiver detects the change in theencoding rule by decoding the first data and reads second data havingcontent corresponding to the change in the encoding rule.

A program according to one aspect of the present invention causes a datatransmitter to implement:

an encoder configured to encode first data to be transmitted, inaccordance with an encoding rule; and

a transmitter configured to transmit the encoded first data.

The encoder makes a change to the encoding rule, encodes the first datain accordance with the change in the encoding rule, and incorporatessecond data having content corresponding to the change in the encodingrule, into the first data.

A program according to one aspect of the present invention causes a datareceiver to implement:

a receiver configured to receive first data encoded in accordance withan encoding rule; and

a decoder configured to decode the first data in accordance with theencoding rule.

If a change is made to the encoding rule in encoding the first data, thedecoder detects the change in the encoding rule by decoding the firstdata and reads second data having content corresponding to the change inthe encoding rule.

According to the above configurations of the present invention, it ispossible to suppress the increase in equipment cost and the reduction indata transmission efficiency associated with the transmission ofmultiple pieces of data.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram showing the configuration of a communication systemfor describing the background of the present invention;

FIG. 2 is a diagram showing the configuration of a communication systemfor describing the background of the present invention;

FIG. 3 is a diagram showing the structure of a transmission frame of thecommunication system shown in FIG. 2;

FIG. 4 is a block diagram showing the configuration of a communicationsystem according to a first embodiment of the present invention;

FIG. 5 is a graph showing encoding of transmission data;

FIG. 6 is a graph showing encoding of transmission data;

FIG. 7A is a diagram showing encoding of transmission data;

FIG. 7B is a diagram showing encoding of transmission data;

FIG. 8A is a graph showing encoding of transmission data;

FIG. 8B is a graph showing encoding of transmission data;

FIG. 9 is a block diagram showing the configuration of a datatransmitter according to a second embodiment of the present invention;and

FIG. 10 is a block diagram showing the configuration of a data receiveraccording to the second embodiment of the present invention.

EXEMPLARY EMBODIMENT First Embodiment

A first embodiment of the present invention will be described withreference to FIGS. 4 to 8B. FIG. 4 is a diagram showing theconfiguration of a communication system according to the presentembodiment. FIGS. 5 to 8B are diagrams showing encoding of transmissiondata according to the present embodiment.

Configuration

As shown in FIG. 4, the communication system according to the presentembodiment includes a transmission circuit 10 included in a datatransmitter and a receiving circuit 20 included in a data receiver andconnected to the transmission circuit 10 through a data transmissionmedium 30.

In the present embodiment, high-speed data (first data) and low-speeddata (second data) are simultaneously transmitted from the transmissioncircuit 10 to the receiving circuit 20 through the single datatransmission medium 30. For example, the high-speed data is primary datato be transmitted from the transmission circuit 10 and is data requiredto be transmitted at high-speed. For example, the low-speed data is datasuch as information about the state of the data transmitter includingthe transmission circuit 10 and is data that is allowed to betransmitted at lower speed than the high-speed data. However, thehigh-speed data and low-speed data need not necessarily have the contentdescribed above, and the relative transmission speeds need not be thosedescribed above.

In the present embodiment, it is assumed that the high-speed data isencoded in accordance with the 8B10B encoding rules and thentransmitted. The 8B10B encoding rules are described below.

8B10B encoding is an encoding scheme for expanding 8-bit data intopreset 10-bit symbol data for transmission. The expansion of 8 bits into10 bits has a disadvantage that the transmission efficiency is reduced;however, 8B10B encoding achieves DC (direct current)-balance andimproves the data transmission quality by controlling the incidence of0s and 1s constituting the bits to 50% and limiting the number ofconsecutive 0s or 1s.

A method for controlling the incidence of 0s and 1s constituting thebits in 8B10B encoding is described below. In 8B10B encoding, theincidence of 0s and 1s constituting the data is controlled according toan encoding rule called “running disparity” (RD). One-code 10-bit datais divided into 6 bits and 4 bits. In each of 6 bits and 4 bits, aweight of +1 is assigned to each data value 1 and a weight of −1 isassigned to each data value 0 so that the sum of weights always is +2,0, or −2 in each of 6 bits and 4 bits. As is understood from this RDcalculation method, RD=+2 means that the number of 1s included in thebits is greater than the number of 0s included in the bits by 2; RD=0means that the number of 1s and the number of 0s are the same; and RD=−2means that the number of 0s is greater than the number of 1s by 2.

Examples of RD in 6-bit data are described below.

110101→RD=+2 (four 1s and two 0s and therefore the sum of the weights is+1×4−1×2=+2)

011000→RD=−2

010101→RD=0

The RD value is calculated for each 6-bit/4-bit data and updated.

In 8B10B encoding, two patterns, a pattern whose RD is 0 or −2, and apattern whose RD is 0 or +2, are prepared for one 10-bit pattern, andeither pattern can be selected.

Assume that RD is −1 at the start of transmission. The starting RD of −1means that the number of 0s is greater than the number of 1s in thepreviously transmitted data. To maintain the DC balance of transmissiondata, a data pattern to be transmitted next must be a data pattern wherethe number of 1s is greater or data pattern where the number of 0s andthe number of 1s are the same. If a data pattern where the number of 0sis greater is transmitted, the DC balance would be lost. Actually, ifthe previous RD is −1, data whose RD value is 0 or +2 is transmitted asthe next pattern. Thus, after transmitting the data, the RD valuebecomes −1 or +1. Similarly, if the previous RD is +1, data whose RDvalue is 0 or −2 is transmitted as the next pattern. Thus, aftertransmitting the data, the RD value becomes −1 or +1. By repeating this,the RD value becomes −1 or +1 at the boundary between 6-bit data and4-bit data

FIG. 5 is a graph showing changes in RD in serial data that has been8B10B-encoded for transmission. The horizontal axis represents the bitarray of the serial data, and the vertical axis represents the RD value.The graph shows two pieces of 8B10B-encoded 10-bit data. Growing linesrepresent data 1, and decreasing lines represent data 0. Each data makesa transition on the lines shown in the graph. The RD value is always −1or +1 at the boundary of 6 bits and 4 bits. The minimum RD value is −3,and the maximum RD value is +3. As shown by arrows in the graph,consecutive is are shown by the straight growing lines and are allowedto extend over up to 5 bits. Similarly, consecutive 0s are shown by thestraight decreasing lines and are allowed to extend over 5 bits.

As seen above, according to an 8B10B encoding calculation rule, RD(calculation value) is set within a range of −3 to +3 and is −1 or +1 atthe boundary between 6 bits and 4 bits. Also, according to an 8B10Bencoding rule, identical signals (1s or 0s) are allowed to extend overup to 5 bits. In other words, consecutive identical signals are notallowed to extend over 6 (a predetermined number of) bits or more.

In the present invention, these 8B10B encoding rules are noted, andlow-speed data corresponding to changes in the 8B10B encoding rules isincorporated into high-speed data and then transmitted. Specifically, RDis noted, and low-speed data is transmitted by setting the RD value to avalue other than −1 and +1 at the boundary between 6 bits and 4 bits.For example, if the RD value is −1 or +1 at the boundary between 6 bitsand 4 bits, low-speed data 0 is transmitted: if the RD value is otherthan −1 and +1 at the boundary between 6 bits and 4 bits, low-speed data1 is transmitted. As seen above, by handling the change in the RD valueas a flag indicating the change in the low-speed data, the low-speeddata can be transmitted through the transmission medium through whichhigh-speed data is being transmitted.

The configuration of the transmission circuit 10 and receiving circuit20 will be described in more detail. As shown in FIG. 4, thetransmission circuit 10 includes an 8B10B encoding circuit 11, an RDcontrol circuit 12, and a parallel/serial conversion circuit 13. Thereceiving circuit 20 includes an 8B10B decoding circuit 21, an RDanalysis circuit 22, and a serial/parallel conversion circuit 23.Function units that perform the same processes as those performed bythese circuits may be constructed by causing arithmetic devices toexecute programs. That is, the transmission circuit 10 and receivingcircuit 20 may be information processing devices including arithmeticdevices, or the functions of the circuits 11 to 13, 21 to 23 may beconstructed by causing arithmetic devices to execute programs.

The 8B10B encoding circuit 11 (encoder) encodes high-speed data inputtedto the transmission circuit 10 in accordance with the 8B10B encodingrules. The 8B10B encoding circuit 11 also changes the RD value inaccordance with low-speed data so that the RD value differs from the RDvalue according to the 8B10B encoding rules. The 8B10B encoding circuit11 then outputs the encoded high-speed data to the parallel/serialconversion circuit 13.

The RD control circuit 12 (encoder) receives low-speed data and causesthe 8B10B encoding circuit 11 to change the RD value at the boundarybetween 6 bits and 4 bits on the basis of whether the received low-speeddata is 0 or 1. That is, the RD control circuit 12 makes changes to the8B10B encoding rules in accordance with the low-speed data, controls theRD value in accordance with the changes in the 8B10B encoding rules, andcauses the 8B10B encoding circuit 11 to incorporate the low-speed datainto the high-speed data during encoding.

The parallel/serial conversion circuit 13 (transmitter) converts theencoded high-speed data outputted from the 8B10B encoding circuit 11into serial data and transmits it to the receiving circuit 20 throughthe data transmission medium 30.

The serial/parallel conversion circuit 23 (receiver) receives the serialdata transmitted from the transmission circuit 10 through the datatransmission medium 30 and converts the serial data into parallel data.Thus, the serial/parallel conversion circuit 23 outputs the samehigh-speed data as the high-speed data inputted to the parallel/serialconversion circuit 13 of the transmission circuit 10, to the 8B10Bdecoding circuit 21.

The 8B10B decoding circuit 21 (decoder) decodes the high-speed data inaccordance with the 8B10B encoding rules and outputs the decodedhigh-speed data. Note that during decoding, the 8B10B decoding circuit21 detects an RD value at the boundary between 6 bits and 4 bitsdifferent from that according to the 8B10B encoding rules. The 8B10Bdecoding circuit 21 then inputs the detected RD value to the RD analysiscircuit 22.

The RD analysis circuit 22 (decoder) checks the RD value detected by the8B10B decoding circuit 21 and detects and outputs the value of thelow-speed data included in the transmitted high-speed data.

Operation

Next, the operation of the transmission circuit 10 and receiving circuit20 will be described. As described above, it is assumed that high-speeddata and low-speed data are transmitted through the single datatransmission medium 30. It is also assumed that the initial value of thelow-speed data to be transmitted is 0; 1 bit of the low-speed datacorresponds to n bytes of the high-speed data; 1 byte of the high-speeddata is 8 bits, which is 1 unit in 8B10B encoding; and a switch between0 and 1 in the low-speed data synchronizes 1 byte of the high-speeddata.

First, the operation in the initial state of transmission will bedescribed. It is assumed that the low-speed data is 0 in the initialstate of transmission, and the state in which the low-speed data doesnot change from 0, which is represents the initial state, is defined asthe initial state.

The high-speed data to be transmitted is inputted to the 8B10B encodingcircuit 11 of the transmission circuit 10. The 8B10B encoding circuit 11encodes the high-speed data in accordance with the 8B10B encoding rules.

The low-speed data to be transmitted, which is the initial value 0, isinputted to the RD control circuit 12. The RD control circuit 12recognizes that the inputted low-speed data is 0, which represents theinitial state. In this case, the RD control circuit 12 makes noinstruction to the 8B10B encoding circuit 11. Thus, the 8B10B encodingcircuit 11 encodes the high-speed data in accordance with the 8B10Bencoding rules.

The encoded high-speed data outputted from the 8B10B encoding circuit 11is inputted to the parallel/serial conversion circuit 13 and convertedinto serial data. The serial data is transmitted to the receivingcircuit 20 through the data transmission medium 30.

In the receiving circuit 20, the received high-speed data is inputted tothe serial/parallel conversion circuit 23, which then converts theserial high-speed data into parallel high-speed data.

The high-speed data outputted from the serial/parallel conversioncircuit 23 is inputted to the 8B10B decoding circuit 21. The 8B10Bdecoding circuit 21 decodes the inputted high-speed data in accordancewith the 8B10B encoding rules. At this time, the 8B10B decoding circuit21 outputs the RD value at the boundary between 6 bits and 4 bits in thehigh-speed data to the RD analysis circuit 22.

The RD analysis circuit 22 recognizes that the transmission is in theinitial state, because the RD value has not been other than −1 and +1since the start of data transmission, and makes no instruction to the8B10B decoding circuit 21. The RD analysis circuit 22 outputs 0 aslow-speed data. The 8B10B decoding circuit 21 handles RD in accordancewith the 8B10B encoding rules, since it has received no instruction fromthe RD analysis circuit 22, and outputs the decoded high-speed data.

FIG. 6 is a graph showing the range of RD in data passing through thedata transmission medium 30 in the initial state of transmission. Thehorizontal axis represents the bit array of serial data, and thevertical axis represents the RD value. FIG. 6 is a graph obtained byextracting outer edge lines from the graph shown in FIG. 5 in order toknow changes in the maximum and minimum values of RD. FIG. 6 shows twopieces of 8B10B-encoded 10-bit data. Since RD repeatedly changes on abit-by-bit basis, similar waveforms are repeatedly formed by the thirddata and later. As in FIG. 5, RD makes a transition between +3 and −3 inthe initial state. The RD value is −1 or +1 at the boundary between 6bits and 4 bits in each 8B10B-encoded 10-bit data. Consecutive 0s or isare allowed to extend over up to 5 bits.

Next, the operation when the low-speed data is changed from 0 to 1 willbe described. When the low-speed data is changed from 0 to 1, the RDcontrol circuit 12 detects that the low-speed data has been changed from0 to 1. The RD control circuit 12 then instructs the 8B10B encodingcircuit 11 to invert the RD value at the boundary between 6 bits and 4bits. The term “invert the RD value” refers to replacing the normal RDvalue −1 or +1 at the boundary between 6 bits and 4 bits with +1 or −1,respectively.

For example, if RD at the boundary between 6 bits and 4 bits is +1, RDis changed to −1, and data whose RD value is 0 or +2 is selected as nexttransmission data. Due to this control, the RD value at the boundarybetween 6 bits and 4 bits becomes +1 or +3. That is, if RD at theboundary between 6 bits and 4 bits is +1 in the initial state, datawhose RD value is 0 or −2 is normally selected as next transmissiondata; however, data whose RD value is 0 or +2 is selected as nexttransmission data in response to the change in the low-speed data. Bychanging the encoding rules in this manner, the range of the RD value ischanged.

Similarly, if RD at the boundary between 6 bits and 4 bits is −1, RD ischanged to +1, and data whose RD value is 0 or −2 is selected as nexttransmission data. Due to this control, the RD value at the boundarybetween 6 bits and 4 bits becomes −1 or −3. That is, if RD at theboundary between 6 bits and 4 bits is −1 in the initial state, datawhose RD value is 0 or +2 is normally selected as next transmissiondata; however, data whose RD is 0 or −2 is selected as next transmissiondata in response to the change in the low-speed data. By changing theencoding rules in this manner, the range of the RD value is changed.Note that RD is inverted as described above only if the low-speed datais changed from 0 to 1; RD is not inverted unless the low-speed data ischanged.

The data outputted from the 8B10B encoding circuit 11 is transmitted tothe receiving circuit 20 through the parallel/serial conversion circuit13 and data transmission medium 30 and then inputted to the 8B10Bdecoding circuit 21 through the serial/parallel conversion circuit 23.

The 8B10B decoding circuit 21 outputs the RD value at the boundarybetween 6 bits and 4 bits to the RD analysis circuit 22. The RD value atthe boundary between 6 bits and 4 bits is +1 or +3, or, −1 or −3. If theRD analysis circuit 22 detects that the RD value is +3 or −3, itdetermines that this value is a value that does not occur in normal8B10B encoding and that RD has been inverted due to the change of thelow-speed data from 0 to 1, and then outputs 1 as low-speed data. Notethat if the RD value is −1 or +1, the RD analysis circuit 22 cannotdetermine whether RD has been inverted on the transmission side, sincethis value is a value that occurs in normal 8B10B encoding. It may taketime for the RD analysis circuit 22 to detect that the RD value is +3 or−3. One measure to detect that the RD value is +3 or −3 due to theinversion of RD is to sufficiently increase the value of the byte numbern of the high-speed data that defines 1 bit of the low-speed data.

When the RD analysis circuit 22 detects that low-speed data 1 has beentransmitted, on the basis of the RD value and notifies the 8B10Bdecoding circuit 21 that RD has been inverted on the transmission side.Since the RD value of +3 or −3 at the boundary between 6 bits and 4 bitsviolates the 8B10B encoding rules, the 8B10B decoding circuit 21normally attempts to raise an error. However, the 8B10B decoding circuit21 has been notified of the inversion of RD by the RD analysis circuit22 and therefore allows the RD value of +3 or −3 and performs controlsuch that such an RD value is not handled as an error. That is, the8B10B decoding circuit 21 8B10B-decodes the high-speed data consideringthe change in RD and outputs the decoded high-speed data.

FIGS. 7A, 7B are graphs showing examples of the range of RD in datapassing through the data transmission medium 30 when the low-speed datais changed from 0 to 1. A dotted line of FIG. 7A shows a case in whichthe RD value is +1 when the low-speed data is changed from 0 to 1, and adotted line of FIG. 7B shows a case in which the RD value is −1 when thelow-speed data is changed from 0 to 1. As is understood from thesediagrams, the RD value is +3 or +1, or −3 or −1 at the boundary between6 bits and 4 bits in each 8B10B-encoded 10-bit data. RD makes atransition between +5 and −1 or between −5 and +1. While the transitionwidth is increased at the instant when the low-speed data is changedfrom 0 to 1, the transition width in the other period is the same asthat in normal 8B10B encoding. Consecutive 0s or is extend over up to 7bits. Consecutive 0s or is extending over 7 bits occur in a positionincluding the boundary between 6 bits and 4 bits when the low-speed datais changed from 0 to 1. Although consecutive 0s or is are allowed toextend over up to 5 bits in normal 8B10B encoding, the increase from 5bits to 7 bits seems to affect the transmission quality to a lesserextent.

As seen above, according to the present embodiment, when encodinghigh-speed data using 8B10B encoding, low-speed data is incorporatedinto the high-speed data by changing the encoding rules, for example, byallowing a change in the range of RD or a change in the number ofconsecutive identical signals. This eliminates the need to separatelyprovide a transmission medium for low-speed data, as well as the need totransmit data in a time-sharing manner. Thus, it is possible to suppressa reduction in the data transmission efficiency while suppressing theequipment cost.

As described above, the receiving circuit 20 detects the changes in theencoding rules and thus detects the low-speed data on the basis of theRD value at the boundary between 6 bits and 4 bits in the 8B10B-encodeddata; however, the low-speed data may be detected from differentinformation in the received data. For example, the receiving circuit 20may detect the changes in the 8B10B encoding rules and thus detect thelow-speed data value in accordance with the maximum transition width ofRD or the number of consecutive identical symbols in the received data.

Next, the operation when the low-speed data is changed from 1 to 0 willbe described. When the low-speed data is changed from 1 to 0, the RDcontrol circuit 12 of the transmission circuit 10 detects that thelow-speed data has been changed from 1 to 0. The RD control circuit 12then notifies the 8B10B encoding circuit 11 that the low-speed data hasbeen changed from 1 to 0.

Thus, if the RD value at the boundary between 6 bits and 4 bits is +1 or−1, the 8B10B encoding circuit 11 inverts RD. If RD is +1, RD of thenext pattern is normally 0 or +2; however, a pattern where RD is 0 or −2is selected as RD of the next pattern due to the inversion of RD. if RDis −1, RD of the next pattern is normally 0 or −2; however, a patternwhere RD is 0 or +2 is selected as RD of the next pattern due to theinversion of RD.

By performing this operation, RD is restored to its original state. Thisis because RD has been inverted due to the change of the low-speed datafrom 0 to 1 and inverted again due to the change of the low-speed datafrom 1 to 0. That is, normal 8B10B encoding is restored, and the RDvalue at the boundary between 6 bits and 4 bits becomes −1 or +1. Theinversion of RD is performed only once when the RD value at the boundarybetween 6 bits and 4 bits is +1 or −1. Note that the inversion of RD isput on hold when the RD value at the boundary between 6 bits and 4 bitsis +3 or −3; the inversion of RD is performed only after the RD valuebecomes +1 or −1 at the boundary between 6 bits and 4 bits in the next10-bit data. That is, even if the low-speed data is changed from 1 to 0,it may take time until RD is inverted.

The data outputted from the 8B10B encoding circuit 11 is transmitted tothe receiving circuit 20 through the parallel/serial conversion circuit13 and data transmission medium 30 and then inputted to the 8B10Bdecoding circuit 21 through the serial/parallel conversion circuit 23.The 8B10B decoding circuit 21 outputs the RD value to the RD analysiscircuit 22. The RD analysis circuit 22 recognizes that 0 has beentransmitted as low-speed data, since the RD value is −1 or +1 at theboundary between 6 bits and 4 bits, and outputs 0 as low-speed data. Asdescribed above, even if the low-speed data is changed from 1 to 0, itmay take time until RD is inverted. One measure to invert RD earlier isto sufficiently increase the value of the byte number n of thehigh-speed data that defines 1 bit of the low-speed data.

The 8B10B decoding circuit 21 receives a notification that the low-speeddata 0 has been transmitted, from the RD analysis circuit 22, performsnormal 8B10B decoding on the high-speed data, and outputs the decodedhigh-speed data.

FIG. 8A is a graph showing the range of RD in data passing through thedata transmission medium 30 when the low-speed data is changed from 1 to0 and is a graph showing a case in which RD is +1 at the boundarybetween 6 bits and 4 bits when the low-speed data is changed from 1 to0. In FIG. 8A, the change range of RD after the change of the low-speeddata from 1 to 0 is shown by a dotted line. As is understood from thisgraph, RD returns to the original 8B10B encoding rules and makes atransition between +3 and −3. Thus, the RD value becomes −1 or +1 at theboundary between 6 bits and 4 bits in the 8B10B-encoded 10-bit data, andconsecutive 0s or is are allowed to extend over up to 5 bits.

FIG. 8B is a graph showing the range of RD in data passing through thedata transmission medium 30 when the low-speed data is changed from 1 to0 and is a graph showing a case in which RD is −1 at the boundarybetween 6 bits and 4 bits when the low-speed data is changed from −1 to0. In FIG. 8B, the change range of RD after the change of the low-speeddata from 1 to 0 is shown by a dotted line. As is understood from thisgraph, RD returns to the original 8B10B encoding rules and makes atransition between +3 and −3. Thus, the RD value becomes −1 or +1 at theboundary between 6 bits and 4 bits in the 8B10B-encoded 10-bit data, andconsecutive 0s or is are allowed to extend over up to 5 bits.

As seen above, even if the low-speed data is changed from 1 to 0, thelow-speed data is incorporated into the high-speed data by makingchanges to the 8B10B encoding rules of the high-speed data.

In the present embodiment, RD of the 8B10B encoding rules is noted.However, as with RD of the 8B10B encoding rules, a change in informationrequired for encoding or a change in the encoding rules may beassociated with the change of the low-speed data. Thus, another type ofdata such as the low-speed data can be incorporated into one type ofdata such as the high-speed data. Also, 8B10B encoding need notnecessarily be performed. Even if one type of data is encoded usinganother encoding scheme, another type of data can be incorporated intothe one type of data by changing the encoding rules. As described above,the present invention is implemented by improving the existing encodingrules; however, it need not be implemented using the existing encodingrules. For example, a new encoding rule for performing encoding asdescribed above may be generated and implemented.

Second Embodiment

Next, a second embodiment of the present invention will be describedwith reference to FIGS. 9, 10. FIGS. 9 and 10 are block diagrams showingthe configuration of a data transmitter and a data receiver according tothe second embodiment. The data transmitter and data receiver accordingto the present embodiment represent an outline of the configuration ofthe transmission circuit 10 and receiving circuit 20 described in thefirst embodiment.

A data transmitter 100 shown in FIG. 9 includes an encoder 101 thatencodes first data to be transmitted, in accordance with an encodingrule and a transmitter 102 that transmits the encoded first data. Thetransmitter 102 makes a change to the encoding rule, encodes the firstdata in accordance with the change in the encoding rule, andincorporates second data having content corresponding to the change inthe encoding rule into the first data.

A data receiver 200 shown in FIG. 10 includes a receiver 201 thatreceives first data encoded in accordance with an encoding rule and adecoder 202 that decodes the first data in accordance with the encodingrule. If the first data is encoded in accordance with a change in theencoding rule, the decoder 202 detects the change in the encoding ruleby decoding the first data and reads second data having contentcorresponding to the change in the encoding rule.

The units 101, 102, 201, and 202 included in the devices 100, 200 areconstructed by causing arithmetic devices included in the devices 100,200 to execute programs.

Using the above configuration, the data transmitter 100 makes a changeto the encoding rule, encodes first data to be transmitted, inaccordance with the change in the encoding rule, incorporates seconddata having content corresponding to the change in the encoding rule,into the first data, and transmits the encoded first data to the datareceiver 200.

The data receiver 200 receives the first data encoded in accordance withthe change in the encoding rule and decodes the first data in accordancewith the change in the encoding rule. At this time, the data receiver200 detects the change in the encoding rule and reads the second datahaving content corresponding to the change in the encoding rule.

Thus, the data transmitter 100 can incorporate the second datacorresponding to the change in the encoding rule in encoding the firstdata. The data receiver 200 can read the second data corresponding tothe change in the encoding rule in decoding the first data. Accordingly,the data transmitter 100 can transmit the second data in such a mannerthat the second data is incorporated in the first data and need nottransmit the data in a time-sharing manner. As a result, it is possibleto suppress the equipment cost and to suppress a reduction in the datatransmission efficiency.

Supplementary Notes

Some or all of the above embodiments can be described as inSupplementary Notes below. Hereafter, there will be outlined theconfigurations of a data transmitter, data receiver, communicationsystem, data transmission method, data receiving method, datatransmission/reception method, and program according to the presentinvention. However, the present invention is not limited to theconfigurations below.

Supplementary Note 1

A data transmitter comprising:

an encoder configured to encode first data to be transmitted, inaccordance with an encoding rule; and

a transmitter configured to transmit the encoded first data, wherein

the encoder makes a change to the encoding rule, encodes the first datain accordance with the change in the encoding rule, and incorporatessecond data having content corresponding to the change in the encodingrule, into the first data.

Supplementary Note 2

The data transmitter according to supplementary note 1, wherein

the encoder makes a change to the encoding rule so as to correspond to achange in the content of the second data and encodes the first data inaccordance with the change in the encoding rule.

Supplementary Note 3

The data transmitter according to supplementary note 1 or 2, wherein theencoder encodes the first data in accordance with the encoding ruleproviding that the first data shall be encoded in such a manner that apredetermined or larger number of consecutive identical signals do notoccur, as well as incorporates the second data into the first data bymaking a change to the encoding rule so that the predetermined or largernumber of consecutive identical signals is allowed to occur and encodingthe first data in accordance with the change in the encoding rule.

Supplementary Note 4

The data transmitter according to any one of supplementary notes 1 to 3,wherein

the encoder encodes the first data in accordance with the encoding ruleproviding that a calculation value calculated in accordance with apredetermined calculation rule on the basis of predetermined symbol datashall fall within a set range, the predetermined symbol data beingobtained by converting a predetermined amount of the first data, as wellas incorporates the second data into the first data by making a changeto the encoding rule so that the calculation value is allowed to falloutside the set range and encoding the first data in accordance with thechange in the encoding rule so that the first data is converted into thesymbol data.

Supplementary Note 5

The data transmitter according to any one of supplementary notes 1 to 4,wherein

the encoder encodes the first data in accordance with the encoding ruleproviding that symbol data obtained by converting subsequent first datashall be set in accordance with a calculation value calculated inaccordance with a predetermined calculation rule on the basis ofpredetermined symbol data obtained by converting a predetermined amountof the first data, as well as sets the symbol data obtained byconverting the subsequent first data, in such a manner that thecalculation value is changed so as to correspond to a change in thecontent of the second data.

Supplementary Note 6

The data transmitter according to any one of supplementary notes 1 to 5,wherein

the encoder encodes the first data in accordance with the encoding ruleproviding that symbol data obtained by converting subsequent first datashall be set in accordance with a value of a running disparitycalculated by 8B10B-encoding the first data, as well as sets the symboldata in accordance with a value obtained by reversing a sign of thevalue of the running disparity, so as to correspond to a change in thecontent of the second data.

Supplementary Note 7

A data receiver comprising:

a receiver configured to receive first data encoded in accordance withan encoding rule; and

a decoder configured to decode the first data in accordance with theencoding rule, wherein

if a change is made to the encoding rule in encoding the first data, thedecoder detects the change in the encoding rule by decoding the firstdata and reads second data having content corresponding to the change inthe encoding rule.

Supplementary Note 8

The data receiver according to supplementary note 7, wherein the decoderreads a change in the content of the second data corresponding to thechange in the encoding rule made in encoding the first data.

Supplementary Note 9

The data receiver according to supplementary note 7 or 8, wherein

by decoding the first data in accordance with the encoding ruleproviding that the first data shall be encoded in such a manner that apredetermined or larger number of consecutive identical signals do notoccur, the decoder detects the change in the encoding rule providingthat the predetermined or larger number of consecutive identical signalsshall be allowed to occur, and reads the content of the second datacorresponding to the change in the encoding rule.

Supplementary Note 10

The data receiver according to any one of supplementary notes 7 to 9,wherein by decoding the first data in accordance with the encoding ruleproviding that a calculation value calculated in accordance with apredetermined calculation rule on the basis of predetermined symbol datashall fall within a set range, the predetermined symbol data beingobtained by converting a predetermined amount of the first data, thedecoder detects the change in the encoding rule providing that thecalculation value shall be allowed to fall outside the set range andreads the content of the second data corresponding to the change in theencoding rule.

Supplementary Note 10.1

A communication system comprising a data transmitter and a datareceiver, wherein

the data transmitter comprises:

-   -   an encoder configured to encode first data to be transmitted, in        accordance with an encoding rule; and    -   a transmitter configured to transmit the encoded first data,

the encoder makes a change to the encoding rule, encodes the first datain accordance with the change in the encoding rule, and incorporatessecond data having content corresponding to the change in the encodingrule, into the first data,

the data receiver comprises:

-   -   a receiver configured to receive the first data encoded in        accordance with the encoding rule; and    -   a decoder configured to decode the first data in accordance with        the encoding rule, and

if a change is made to the encoding rule in encoding the first data, thedecoder detects the change in the encoding rule by decoding the firstdata and reads second data having content corresponding to the change inthe encoding rule.

Supplementary Note 11

A data transmission method comprising:

encoding, by a data transmitter, first data to be transmitted, inaccordance with an encoding rule; and

transmitting, by the data transmitter, the encoded first data, wherein

the data transmitter makes a change to the encoding rule, encodes thefirst data in accordance with the change in the encoding rule, andincorporates second data having content corresponding to the change inthe encoding rule, into the first data.

Supplementary Note 12

The data transmission method according to supplementary note 11, wherein

the data transmitter makes a change to the encoding rule so as tocorrespond to a change in the content of the second data and encodes thefirst data in accordance with the change in the encoding rule.

Supplementary Note 13

The data transmission method according to supplementary note 11 or 12,wherein

the data transmitter encodes the first data in accordance with theencoding rule providing that the first data shall be encoded in such amanner that a predetermined or larger number of consecutive identicalsignals do not occur, as well as incorporates the second data into thefirst data by making a change to the encoding rule so that thepredetermined or larger number of consecutive identical signals isallowed to occur and encoding the first data in accordance with thechange in the encoding rule.

Supplementary Note 14

The data transmission method according to any one of supplementary notes11 to 13, wherein the data transmitter encodes the first data inaccordance with the encoding rule providing that a calculation valuecalculated in accordance with a predetermined calculation rule on thebasis of predetermined symbol data shall fall within a set range, thepredetermined symbol data being obtained by converting a predeterminedamount of the first data, as well as incorporates the second data intothe first data by making a change to the encoding rule so that thecalculation value is allowed to fall outside the set range and encodingthe first data in accordance with the change in the encoding rule sothat the first data is converted into the symbol data.

Supplementary Note 15

The data transmission method according to any one of supplementary notes11 to 14, wherein

the data transmitter encodes the first data in accordance with theencoding rule providing that symbol data obtained by convertingsubsequent first data shall be set in accordance with a calculationvalue calculated in accordance with a predetermined calculation rule onthe basis of predetermined symbol data obtained by converting apredetermined amount of the first data, as well as sets the symbol dataobtained by converting the subsequent first data, in such a manner thatthe calculation value is changed so as to correspond to a change in thecontent of the second data.

Supplementary Note 16

The data transmission method according to any one of supplementary notes11 to 15, wherein

the data transmitter encodes the first data in accordance with theencoding rule providing that symbol data obtained by convertingsubsequent first data shall be set in accordance with a value of arunning disparity calculated by 8B10B-encoding the first data, as wellas sets the symbol data in accordance with a value obtained by reversinga sign of the value of the running disparity, so as to correspond to achange in the content of the second data.

Supplementary Note 17

The data transmission method according to any one of supplementary notes11 to 16, further comprising:

receiving, by a data receiver, the first data encoded in accordance withthe encoding rule; and

decoding, by the data receiver, the first data in accordance with theencoding rule, wherein

if a change is made to the encoding rule in encoding the first data, thedata receiver detects the change in the encoding rule by decoding thefirst data and reads second data having content corresponding to thechange in the encoding rule.

Supplementary Note 18

The data transmission method according to supplementary note 17, wherein

the data receiver reads a change in the content of the second datacorresponding to the change in the encoding rule made in encoding thefirst data.

Supplementary Note 19

The data transmission method according to supplementary note 17 or 18,wherein

by decoding the first data in accordance with the encoding ruleproviding that the first data shall be encoded in such a manner that apredetermined or larger number of consecutive identical signals do notoccur, the data receiver detects the change in the encoding ruleproviding that the predetermined or larger number of consecutiveidentical signals shall be allowed to occur and reads the content of thesecond data corresponding to the change in the encoding rule.

Supplementary Note 20

The data transmission method according to any one of supplementary notes17 to 19, wherein

by decoding the first data in accordance with the encoding ruleproviding that a calculation value calculated in accordance with apredetermined calculation rule on the basis of predetermined symbol datashall fall within a set range, the predetermined symbol data beingobtained by converting a predetermined amount of the first data, thedata receiver detects the change in the encoding rule providing that thecalculation value shall be allowed to fall outside the set range andreads the content of the second data corresponding to the change in theencoding rule.

Supplementary Note 21

A data receiving method comprising:

receiving, by a data receiver, first data encoded in accordance with anencoding rule; and

decoding, by the data receiver, the first data in accordance with theencoding rule, wherein

if a change is made to the encoding rule in encoding the first data, thedata receiver detects the change in the encoding rule by decoding thefirst data and reads second data having content corresponding to thechange in the encoding rule.

Supplementary Note 22

A data transmission/reception method performed by a communication systemincluding a data transmitter and a data receiver, the method comprising:

encoding, by a data transmitter, first data to be transmitted, inaccordance with an encoding rule;

transmitting, by the data transmitter, the encoded first data, whereinthe data transmitter makes a change to the encoding rule, encodes thefirst data in accordance with the change in the encoding rule, andincorporates second data having content corresponding to the change inthe encoding rule, into the first data;

receiving, by a data receiver, the first data encoded in accordance withthe encoding rule; and

decoding, by the data receiver, the first data in accordance with theencoding rule, wherein if a change is made to the encoding rule inencoding the first data, the data receiver detects the change in theencoding rule by decoding the first data and reads second data havingcontent corresponding to the change in the encoding rule.

Supplementary Note 23

A computer-readable storage medium storing a program for causing a datatransmitter to implement:

an encoder configured to encode first data to be transmitted, inaccordance with an encoding rule; and

a transmitter configured to transmit the encoded first data, wherein theencoder makes a change to the encoding rule, encodes the first data inaccordance with the change in the encoding rule, and incorporates seconddata having content corresponding to the change in the encoding rule,into the first data.

Supplementary Note 24

A computer-readable storage medium storing a program for causing a datareceiver to implement:

a receiver configured to receive first data encoded in accordance withan encoding rule; and

a decoder configured to decode the first data in accordance with theencoding rule, wherein

if a change is made to the encoding rule in encoding the first data, thedecoder detects the change in the encoding rule by decoding the firstdata and reads second data having content corresponding to the change inthe encoding rule.

The above programs are stored in a storage device or computer-readablestorage medium. For example, the storage medium is a portable mediumsuch as a flexible disk, optical disk, magneto-optical disk, orsemiconductor memory.

While the present invention has been described with reference to theembodiments and the like, the present invention is not limited thereto.Various changes understandable by those skilled in the art can be madeto the configuration or details of the invention of the presentapplication without departing from the scope of the invention.

DESCRIPTION OF REFERENCE NUMERALS

-   10 transmission circuit-   11 8B10B encoding circuit-   12 RD control circuit-   13 parallel/serial conversion circuit-   20 receiving circuit-   21 8B10B decoding circuit-   22 RD analysis circuit-   23 serial/parallel conversion circuit-   30 data transmission medium-   100 data transmitter-   101 encoder-   102 transmitter-   200 data receiver-   201 receiver-   202 decoder

The invention claimed is:
 1. A data transmitter comprising: an encoderconfigured to: encode a first portion of first data to be transmitted,in accordance with an encoding rule; change the encoding rule accordingto second data to be transmitted; and encode a second portion of thefirst data with the changed encoding rule, the change in the encodingrule indicating content of the second data; and a transmitter configuredto transmit the encoded first portion of first data and the encodedsecond portion of the first data.
 2. The data transmitter according toclaim 1, wherein the encoder is further configured to make a change tothe encoding rule so as to correspond to a change in the content of thesecond data and encode the first data in accordance with the change inthe encoding rule.
 3. The data transmitter according to claim 1, whereinthe encoder is further configured to encode the first data in accordancewith the encoding rule providing that the first data shall be encoded insuch a manner that a number of consecutive identical signals equal to orlarger than a predetermined number do not occur, and incorporate thesecond data into the first data by making a change to the encoding ruleso that the number of consecutive identical signals equal to or largerthan the predetermined number is allowed to occur and encoding the firstdata in accordance with the change in the encoding rule.
 4. The datatransmitter according to claim 1, wherein the encoder is furtherconfigured to encode the first data in accordance with the encoding ruleproviding that a calculation value calculated in accordance with apredetermined calculation rule based on predetermined symbol data shallfall within a set range, the predetermined symbol data being obtained byconverting a predetermined amount of the first data, and incorporate thesecond data into the first data by making a change to the encoding ruleso that the calculation value is allowed to fall outside the set rangeand encode the first data in accordance with the change in the encodingrule so that the first data is converted into the predetermined symboldata.
 5. The data transmitter according to claim 1, wherein the encoderis further configured to encode the first data in accordance with theencoding rule providing that symbol data obtained by converting thesecond portion of the first data shall be set in accordance with acalculation value calculated in accordance with a predeterminedcalculation rule based on predetermined symbol data obtained byconverting a predetermined amount of the first data, and set the symboldata obtained by converting the second portion of the first data, insuch a manner that the calculation value is changed so as to correspondto a change in the content of the second data.
 6. The data transmitteraccording to claim 1, wherein the encoder is further configured toencode the first data in accordance with the encoding rule providingthat symbol data obtained by converting the second portion of first datashall be set in accordance with a value of a running disparitycalculated by 8B10B-encoding the first data, and set the symbol data inaccordance with a value obtained by reversing a sign of the value of therunning disparity, so as to correspond to a change in the content of thesecond data.
 7. A data receiver comprising: a receiver configured toreceive a first portion of first data encoded in accordance with anencoding rule; and a decoder configured to: decode the first portion ofthe first data in accordance with the encoding rule; detect a change inthe encoding rule; decode a second portion of the first data inaccordance with the changed encoding rule; and determine content ofsecond data based on the detection of the change in the encoding rule.8. The data receiver according to claim 7, wherein the decoder isfurther configured to determine a change in the content of the seconddata corresponding to the change in the encoding rule made in encodingthe first data.
 9. The data receiver according to claim 7, wherein bydecoding the first data in accordance with the encoding rule providingthat the first data shall be encoded in such a manner that consecutiveidentical signals equal to or larger than a predetermined number do notoccur, the decoder detects the change in the encoding rule providingthat the number of consecutive identical signals equal to or larger thanthe predetermined number shall be allowed to occur and reads the contentof the second data corresponding to the change in the encoding rule. 10.The data receiver according to claim 7, wherein by decoding the firstdata in accordance with the encoding rule providing that a calculationvalue calculated in accordance with a predetermined calculation rulebased on predetermined symbol data shall fall within a set range, thepredetermined symbol data being obtained by converting a predeterminedamount of the first data, the decoder detects the change in the encodingrule providing that the calculation value shall be allowed to falloutside the set range and reads the content of the second datacorresponding to the change in the encoding rule.
 11. A datatransmission method comprising: encoding, by a data transmitter, a firstportion of first data to be transmitted, in accordance with an encodingrule; changing, by the data transmitter, the encoding rule according tosecond data to be transmitted; encoding, by the data transmitter, asecond portion of the first data with the changed encoding rule, thechange in the encoding rule indicating content of the second data; andtransmitting, by the data transmitter, the encoded first portion offirst data and the encoded second portion of the first data.
 12. Thedata transmission method according to claim 11, wherein the datatransmitter makes a change to the encoding rule so as to correspond to achange in the content of the second data and encodes the first data inaccordance with the change in the encoding rule.
 13. The datatransmission method according to claim 11, wherein the data transmitterencodes the first data in accordance with the encoding rule providingthat the first data shall be encoded in such a manner that a number ofconsecutive identical signals equal to or larger than a predeterminednumber do not occur, as well as incorporates the second data into thefirst data by making a change to the encoding rule so that the number ofconsecutive identical signals equal to or larger than a predeterminednumber is allowed to occur and encoding the first data in accordancewith the change in the encoding rule.
 14. The data transmission methodaccording to claim 11, wherein the data transmitter encodes the firstdata in accordance with the encoding rule providing that a calculationvalue calculated in accordance with a predetermined calculation rulebased on predetermined symbol data shall fall within a set range, thepredetermined symbol data being obtained by converting a predeterminedamount of the first data, as well as incorporates the second data intothe first data by making a change to the encoding rule so that thecalculation value is allowed to fall outside the set range and encodingthe first data in accordance with the change in the encoding rule sothat the first data is converted into the predetermined symbol data. 15.The data transmission method according to claim 11, wherein the datatransmitter encodes the first data in accordance with the encoding ruleproviding that symbol data obtained by converting the second portion offirst data shall be set in accordance with a calculation valuecalculated in accordance with a predetermined calculation rule based onpredetermined symbol data obtained by converting a predetermined amountof the first data, and sets the symbol data obtained by converting thesecond portion of the first data, in such a manner that the calculationvalue is changed so as to correspond to a change in the content of thesecond data.
 16. The data transmission method according to claim 11,wherein the data transmitter encodes the first data in accordance withthe encoding rule providing that symbol data obtained by converting thesecond portion of the first data shall be set in accordance with a valueof a running disparity calculated by 8B10B-encoding the first data, aswell as sets the symbol data in accordance with a value obtained byreversing a sign of the value of the running disparity, so as tocorrespond to a change in the content of the second data.
 17. The datatransmission method according to claim 11, further comprising:receiving, by a data receiver, the first portion of the first dataencoded in accordance with the encoding rule; and decoding, by the datareceiver, the first portion of the first data in accordance with theencoding rule; detecting a change in the encoding rule; decoding asecond portion of the first data in accordance with the changed encodingrule; and determining content of second data based on the detection ofthe change in the encoding rule.
 18. The data transmission methodaccording to claim 17, wherein the data receiver reads a change in thecontent of the second data corresponding to the change in the encodingrule made in encoding the first data.
 19. The data transmission methodaccording to claim 17, wherein by decoding the first data in accordancewith the encoding rule providing that the first data shall be encoded insuch a manner that a number of consecutive identical signals equal to orlarger than a predetermined number do not occur, the data receiverdetects the change in the encoding rule providing that the consecutiveidentical signals equal to or larger than a predetermined number shallbe allowed to occur and reads the content of the second datacorresponding to the change in the encoding rule.
 20. The datatransmission method according to claim 17, wherein by decoding the firstdata in accordance with the encoding rule providing that a calculationvalue calculated in accordance with a predetermined calculation rulebased on predetermined symbol data shall fall within a set range, thepredetermined symbol data being obtained by converting a predeterminedamount of the first data, the data receiver detects the change in theencoding rule providing that the calculation value shall be allowed tofall outside the set range and reads the content of the second datacorresponding to the change in the encoding rule.